In constructing electronic devices using integrated circuits, flexibility in connecting integrated circuits to other portions of an electronic device may be useful in designing, prototyping, upgrading and repairing such devices. For instance, during initial design or prototype builds, a designer may wish to exchange an integrated circuit with others. This may be more easily facilitated using a plug-in interconnect than a soldered interconnect. Similarly, after manufacture or purchase of a circuit board or electronic device, a plug-in interconnect may allow economical upgrade or repair.
A pin grid array (PGA) interconnect is a known plug-in interconnect, which may be used for attaching integrated circuits to printed circuit boards. PGA pin and socket solutions are typically limited to low-frequency interconnections, which may also include power and ground connections. The low-frequency signal limitation may stem from an inconsistency of transmission length associated with the pins seated in the sockets, and also from stubs that may result from the attachment of the pins and sockets to their respective substrates. At higher frequencies, including the giga-hertz range, the PGA pin-sockets may show length inconsistencies and the stubs at their substrate attachments may act as small antennas, emitting electrical interference or “noise”, often referred to as electromagnetic interference (EMI) or radio frequency interference (RFI).
Land grid array (LGA) systems may overcome some of the above limitations with use of alternative interconnect configurations. Landing pads may be formed on opposite facing surfaces of separate substrates, and a polymer compound material that is embedded with metallized particles may be configured in columnar structures and compressed for conductivity between the opposing landing pads. Accordingly, the metallized particle interconnects (MPI) with landing pads may avoid the stub and length variance difficulties of the pin/socket substrate assemblies.
In the MPI system, elastic polymer material with embedded metallized particles may be formed into small columns that may conduct as an interconnection when compressed. The columns may be supported in an insulating material such as polyimide. The polyimide with the MPI columns may then be sandwiched between first and second substrates—e.g., such as a first substrate to interface a circuit board and a second substrate over the first to seat an integrated circuit(s). These assemblies are typically held together between a base plate under the printed circuit board and a heat sink over the integrated circuit(s).
To achieve a desired electrical conductivity, the MPI columns must typically be compressed and may require a compression force of tens of grams per column. With a large array of MPI columns, a collective compressive force on the order of 50 or 60 pounds might be required.